This invention relates generally to an apparatus for measuring grain loss in harvesting machines, and more particularly, to an apparatus that may be used for measuring grain losses in harvesting machines, lost grain being that grain which is lost by way of either being entrained in the straw which is discharged from the combine separating mechanism to the ground or by way of being discharged together with chaff and other impurities from the combine cleaning apparatus.
Throughout this specification the reference to "grain" is intended to refer to that part of the crop which is threshed and separated from the discardable part of the crop material which is referred to as "straw". In the following description terms such as "forward", "rearward", "left", "right" etc. are used which are words of convenience and which are not to be construed as limiting terms.
Grain loss monitors for harvesting machines are known and these attempt to monitor the amount of grain which is lost by way of being entrained with the straw, chaff and other debris and not separated therefrom. To date, no grain loss monitor has been provided which is able to provide an indication, in absolute terms, of the magnitude of the actual grain loss that is occurring during the harvesting operation. Known monitors have only been able to provide some indication which varies more-or-less proportionally with the variations in the magnitude of the actual grain losses without however having been able to establish the correlation factor between this indication and the actual losses. These known grain loss monitors rely on impact detectors to "count" a fraction of the grain which is being discharged with the straw, chaff and other debris at the back of the machine without knowing however the exact relative proportion between this fraction and the total actual losses.
A number of problems are encountered over and above the basic problem of not being able to provide an exact measurement of the amount of grain being lost. One of the ancillary problems is that known detectors are unable to distinguish with any assurance between impacts occasioned by grain and those occasioned by pieces of straw having a nodule at one end thereof and which can be "seen" by a detector as a grain kernal. This problem is particularly critical in wet grain conditions.
Another problem with known grain loss monitors is the relatively complex procedure which has to be adopted to set up the monitor in the first place. Apart from having to operate a plurality of controls according to the type of crop and the condition of the crop being harvested (the latter being likely to change anyway as one proceeds with the harvesting operation), the operator has to calibrate the monitor to some extent by way setting the relevant controls and then physically checking the straw, chaff and other debris which is being discharged by the machine and using his practiced eye to decide whether or not the extent of grain loss is acceptable. If it is not, then the controls are reset and a further check is made.
When the operator decides that the grain loss is acceptable, he then attempts to operate the machine so as to keep the grain loss monitor "reading" at the same value. If the operator does not use his practiced eye to effect this calibration of a known grain loss monitor, then grain loss can be relatively high even when the monitor might indicate otherwise. This is because, if a crop being harvested is of a type or is in a condition such that it is difficult to separate grain from the straw in which it is entrained, the detectors will detect very little grain because, if the latter is not properly separated from the straw, then it will not impact the detector in the form necessary to be "counted."
Accordingly, in this harvesting situation, the grain loss monitor will indicate that the grain loss is minimal and probably zero when quite the reverse situation may pertain. It will also be appreciated that, in a crop or crop condition which results in an easier separation of grain from the straw, the grain loss monitor will indicate that there is grain loss which, while being true, is at a level which is usually significantly less than for the crop or crop condition having the characteristic of being difficult to separate the grain from the straw. This thus is the reason why the practiced eye of the operator is required for calibration purposes.
It further also will be appreciated that, even with the calibration as described above, the grain loss monitor still does not provide a "reading" in absolute figures of the magnitude of the actual losses. Instead, this monitor "reading" only indicates whether or not the actual losses are at a generally acceptable level. In addition thereto, variations in the grain loss monitor "reading" further also may be interpreted to mean that the actual grain losses vary more-or-less accordingly, i.e. increase or decrease together with an increased, respectively decreased monitor "reading" even though there appears not necessarily to exist a linear correlation therebetween.
Accordingly, it would be desirable to overcome not only this problem of calibration experienced with known grain loss monitors but, more importantly, to provide an apparatus which will measure actual loss of grain.